It has long been recognised that one of the most frequently encountered medical emergencies is loss of cardiorespiratory function necessitating resuscitation.
Basic cardiopulmonary resuscitation (`Basic CPR`) refers to maintenance of essential life functions in situations of cardiorespiratory arrest, i.e. where spontaneous breathing is absent and no pulse is present due to inadequate cardiac output. In adults, this arrest is most often due to `cardiac arrest` (e.g. myocardial infarction), whereas in children it is more often secondary to `respiratory arrest` or hypoxia e.g. asphyxia.
Basic CPR is the accepted technique out of hospital where advanced life support systems are not available. Examples of situations where basic CPR is essential include drowning, trauma, drug overdose, and myocardial infarction.
It has been shown that Basic CPR, when performed adequately, will satisfy the physiological criterion of maintaining delivery of oxygen and nutrients to vital tissues, in order to preserve their cellular function.
Basic CPR can be performed by two techniques: (a) `Old` CPR and (b) `New` CPR, which will be described in more detail as follows:
(a) `Old` CPR is well-established in the medical literature. PA1 (b) `New` CPR has been described only very recently. It follows the same basic theory as `old` CPR, except that it recommends the simultaneous performance of both external cardiac compression and ventilation, resulting in a greatly enhanced forward blood flow and cardiac output, because of a greater increase in intrathoracic pressure that is transmitted in the heart. It is possible that coronary blood flow is increased and that myocardial perfusion is significantly improved. PA1 a) Simple to understand and perform. PA1 b) Effective in maintaining an adequate cardiac output and respiration. PA1 c) Acceptable to the user. PA1 a) cardiac massage, PA1 b) artificial respiration, and PA1 c) suction of secretions from the airway, without placing the operator in contact with the patient's secretions until professional assistance arrives. The device is suitable for administering either air or an air-oxygen mixture of desired composition.
The basic technique where no specialised equipment is available is to clear the airways of solid or fluid matter, position the patient supine with neck extended and tongue brought forward, and then to apply positive pressure breathing at a rate of 10-15/min (e.g. mouth-to-mouth, or by mask), together with external cardiac compression at a rate of 80-100/min.
This ideally requires two trained operators. Although it can be performed by one trained operator, this is much less efficient due both to the technique itself and to the physical strain involved.
The basis for the technique is that the increase in intrathoracic pressure is transmitted to the heart; when performed properly, it has been shown to generate 15-25% of normal cardiac output. This results in predominantly `forward` blood flow to the brain, as the valves in the great veins in the neck prevent reverse flow.
CPR is known among the general (non-medical) community to varying degrees, and training courses are offered by various organizations. For example, in Seattle, U.S.A., a community program has resulted in training of a very high proportion of the community.
In order for a CPR method to be of use, it must be
The performance of mouth-to-mouth resuscitation is a particular problem. Lay persons with some training in first aid seem less likely to hesitate in an emergency to apply mouth-to-mouth ventilation (Safar, P., in "Critical Care, State of the Art" ed. W.C. Shoemaker and L.L. Thompson S1-S65 (1981)). However, it seems that hospital personnel are more reluctant, as in a recent study up to 30% of 70 subjects would at times make a judgement in the community setting prejudicial to a victim's survival (Lawrence, P.J. and N. Sivaneswaran, (1985): Med. J. Aust. 143 443-446). In particular, it is well-known that people are reluctant to administer mouth-to-mouth resuscitation to patients who have vomited, have purulent sputum or copious secretions, or who are known to be infected. In the study already cited, only 49 (70%) of the 70 subjects were prepared to perform mouth-to-mouth ventilation for a victim in the community setting. Five subjects (7%) stated that they would not be prepared to use this method while 16 (23%) would use it only selectively, according to such influences as age of the victim, the presence of vomitus, evidence of intravenous drug abuse, and state of hygiene.
The responses for resuscitation in the hospital setting were markedly different. Only 36 (51%) were prepared to use mouth-to-mouth resuscitation on a "clean" victim, and when vomitus or infected secretions were present only nine (13%) would be prepared to use mouth-to-mouth. Mouth-to-mask ventilation was accepted by 41 (59%) for all patients. The addition of a mouthpiece resulted in acceptance by all subjects for clean patients and by 67 (96%) for dirty patients. The addition of a bacterial filter resulted in 100% acceptance under all circumstances.
It is noteworthy, however, that this study was carried out before the recent very widespread publicity given to the acquired immune deficiency syndrome (AIDS). One may assume even less willingness would be found now, in spite of the absence of reported cases of AIDS transmission by this route. However, the AIDS-related HTLV-III virus is found in the saliva of both symptomatic and asymptomatic high-risk groups, (Groopman J.E., S.Z. Salahuddin, M.G. Sarngadharan et al. (1984): Science 226 447-449) and groups such as ambulance officers and police have refused to administer mouth-to-mouth resuscitation to those at risk of or suffering from AIDS.
Thus most potentially preventable deaths occurring in outside-the-hospital situations occur nowadays either because of ignorance of Basic CPR, inadequate knowledge of its applications, or aversion to its use because of the presence of secretions or vomitus, or the fear of transmissible disease, particularly AIDS.
The existing recommendations for emergency ventilation are for mouth-to-mouth ventilation or, if equipment is used, mouth-to-face mask ventilation, until the airway is assured by intubation (Standards and guidelines for cardiopulmonary resuscitation (CPR) and emergency cardiac care (ECC) JAMA--Volume 255, No. 21, Published Jun. 6, 1986 (pages 2905-2984). This seems not to have been accepted into current practice in many hospitals, where a variety of devices may confront a person attempting resuscitation. Pulmonary ventilation is frequently inadequate when these devices are used during CPR, unless special instruction is given, and one frequently used system, bag-valve-mask ventilation, had a 97% failure rate even after instruction (Lawrence and Sivaneswaran, op. cit).
Internationally accepted guidelines for CPR recommend that if equipment is to be used, then mouth-to-mask ventilation should be used until intubation is carried out, either endotracheally or with an oesophageal obturator airway (JAMA, op. cit.).
However, most mouth-to-mask methods require the operator to hold the mask to the patient's face using both hands. Consequently a second operator must be present if cardiac massage is to be applied, which gravely limits this method. More commonly such emergencies occur in situations where face masks are not available.